Magazine

Jan - Mar 1992

Shortly after midnight on December 14, 1991, a seismograph at Twizel recorded shock waves which in 20 seconds reached the magnitude of a 3.9 earthquake. But this was no earthquake. Seventy-five kilometres away, the top of Mt Cook was collapsing. An awesome rock avalanche had let rip, dislodging 14 million cubic metres of rock buttress and glaciers, and sending them on a wild cascade 2720 metres down the mountain.
The majestic East Face, the summit of New Zea­land's highest mountain, was transformed. A giant had toppled in a frantic hail of rock, snow and ice which at times reached speeds of 450 kilometres an hour. Twizel recorded the faint falling of rocks for hours afterwards.
The avalanche also dislodged one of the more easily assimilated pieces of Kiwi trivia. Generations had learned that Mt Cook was 12,349 feet high—so easy to remember, it seemed incontrovertible. Its metric equivalent, 3764 metres, never sat so easily in the cerebral filing system.
Now Aorangi-Mt Cook is 10 metres shorter, and shrinking. Still the Cloud Piercer, but immanently fallible.
The mountain is falling down under its own weight, but scientists are matter-of-fact about this. "All our mountains are unstable, and a mountain falling down is not an unusual phenomenon,"Christchurch DSIR geomorphologist, Dr Mauri McSaveney says. "It's something that's been happening for thousands of years."
On its upper slopes, the mountain does not have the glacial ice flow which causes erosion lower down. Rock falls are the only means of erosion. The December avalanche did away with the theory that the high peaks of Cook were high because their rock was slightly stronger than that lower down.
Like many mountains in this area of the Southern Alps, Mt Cook is made of sedimentary rock called greywacke—very hard sandstone and siltstone which is about 200 million years old. The giant rock fall gave scientists a rare opportunity to look inside the mountain, and Mc­Saveney was amazed at how fractured and weak it really was. The loose, shattered rock he saw was what mountaineers call "Weet-Bix". Mt Cook is not made of stern stuff.
"Yet if anyone had asked me on the Friday (13th December), 'How safe is Mt Cook?' I'd have said, 'Perfectly safe'," says McSaveney.
Veteran Cook climber Rob Hall agrees.
That Friday there were two climbing parties in Plateau Hut, about four kilometres from the sum­mit.
Alarms were set for midnight. David Ellis and Nick Shearer planned to climb Mt Tasman. Hall and his three companions were preparing to climb Mt Cook via Zurbriggen Ridge. Their timing was impeccable. A decision to leave any earlier and they would have been right in the path of the avalanche.
"It would have been a spectacular way to go." Hall can now laugh.
Awaking at midnight, Hall's first thought was that the wind had come up. He'd gone to bed on a clear, moonless night. Ellis went outside. He, too, heard the sound of wind, but, eerily, there was no air movement. The climbers heard a loud rumbling sound. Hall thought it might be an icefall in the Hochstetter.
From the but windows they gazed at the peaks outlined against a black sky.
"Suddenly, I saw huge yellowy sparks, and realised that it was not ice falling—it was rocks," says Hall. To Ellis, the sparks and bright green flashes looked like incendiary bombs falling.
The climbers were vious to danger, more fascinated than frightened. Sometimes there are strange sounds in the mountains. Where there are glaciers, rock avalanches are quite common.
"We just didn't realise the scale of it," says Hall, "that by morning there'd be a pile of rock at the bottom of the mountain."
Hall's party changed tack and decided to climb nearby Mt Dixon.
Ellis and Shearer set out across the Grand Plateau away from the sound of rumbling and grinding rocks. By torchlight they could see a fine mist. As they crossed the northern end of the Plateau they began to cough up dust.
"As dawn approached we looked across, and there was this huge dust cloud over the East Face. It hung there until nearly 10 o'clock," says Ellis.
Daylight revealed that the avalanche had crossed within 500 metres of the but as it curled around and roared its way down the Hochstetter.
On the ridge of Mt Dixon, Hall surveyed the damage. "The scar looked enormous—as if a blanket had spewed down the mountainside and turned it from white to black."
The 500-metre scar can be seen from some points on the Canterbury Plains, 100 kilometres from the mountain.
Bryan Moore was the first to brave Mt Cook after the avalanche. On January 2, 1992, he went up the Hooker Face in perfect conditions. Perched on the thin inclined sliver of ice at the top, he gingerly sur­veyed the wasteland—the "acres and acres" of loose rock which is now the East Face.
By winter, snow will dignify the Grand Plateau snowfields once more, hiding the chaos beneath. Winter will also bring a veneer of ice and snow to the jagged East Face, but some five years will pass before glacier ice flow carries the last of the debris through the now defiled Hochstetter icefall, and it will be many years before thick glacier ice forms in the scar.
Why the avalanche happened on a calm, clear night is a mystery. The mountain does not yield up its secrets easily, and history is of little help. In 1873 there was a rock fall of similar magnitude on Mt Cook, but McSaveney can find only one reference to it in a scientific journal. It seems it happened in a period where no-one took much notice of such things.
The winter of 1991 was one of the snowiest on record. The most plausible theory is that the movement of ice may have plucked rocks from the mountain­side. If all or part of an apron glacier clinging to a mountain face falls, it frequently takes some rock with it. If this rock is supporting an unstable buttress, the "chock" stone may be dislodged. Then it's a case of "chocks away!" But any evidence that this happened in the December avalanche would have been swiftly buried.
McSaveney is certain of one thing: it will happen again. The most frustrating thing is not knowing when. "It might take a century, it might happen next week."
The top of the East Face scar stands at a 70-degree angle. To remain stable, it needs to be around 55 degrees. Bits will continue to fall off, or there'll be another big fall. The mountain peak will shrink as the sharp feathered edge of ice is weathered to a stable shape. So, for some time to come, it's pencils only in the record books.
From the Hermitage, Cook's peaks look little different—a relief, no doubt, to the souvenir sellers. From Okarito in South Westland the moun­tain's profile is dramatically altered. And if a glacier forms in the face of the scar, the East Face will provide a fresh challenge to the dauntless climber.
"It will need a techni­cally competent climber," says McSaveney. "This will be a mighty ice climb."
The new East Face conqueror will need to be sure of one thing: that no rocks have fallen for quite some time. "It could be a rather long wait," McSaveney says drily.

For the second time in less than two years, a tropical cyclone has hammered Western Samoa. In February 1990 tropical cyclone Ofa killed seven people and caused $300 million damage to this island nation of 160,000 people. The island had not fully recov­ered when cyclone Val struck in December last year, killing 12 people and causing damage estimated at $535 million.

It takes six hours' walking to reach Port Craig from the Bluecliffs road end. Seven hours if the tide is in. Seven hours of boulders, hills, streams, beach and wet bush.
Finally, there's a bit of a clearing, a trampers' but and a few rotting wharf piles down on the beach. It's difficult to imagine that one generation ago this isolated headland at the southern tip of the South Island was the site of the largest and most modern timber mill in the country.
Port Craig is at the western end of Te Waewae Bay, 45 kilometres from Tuatapere. Minty Hughes went to school there, in what is now the trampers' hut. He shows a photograph of himself standing with other school children in front of the building. There are more photos: family homes, singlemen's huts, a billiard hall, cook house—and the huge mill.
Minty's 79-year-old eyes gain added brightness when the album flicks over to pictures of the bush loco­motives and steam haulers. Now living in Invercargill, the dedicated steam hobbyist has spent the last two-and-a-half years building a working replica of the mill's Lidgerwood steam hauler.
The Lidgerwood was the largest steam hauler used in the New Zealand bush, and was built in North America. Mounted on rails and weighing 90 tonnes, it pulled logs along a skyline cable held up by two rimu trunks spliced together to form a 30 metre spar. It had a vertical boiler connected to two engines capable of producing 128 horsepower, compared to the 10 to 20 horsepower capacity of ground haulers of that period. The two engines drove a total of ten winches.
Minty's older brother worked as whistle boy for the Lidgerwood, signalling the hauler driver to slacken or tighten the wire ropes which ran off the winch drums. Seventeen men worked with the Lidgerwood: fellers with crosscut saws, trackers to clear lines for the trees, sniggers to hook the logs on the wires, riggers for the spars, and the driver and fireman. The hauler pulled mainly rimu logs from the hillsides to a radius of half a mile, until a complete circle had been worked.
Later, the Lidgerwood was replaced by six ground haulers, each manned by five men and one boy. Minty left school at 14 to be whistle boy on one crew.
Logs were pulled from the hauler sites to the mill by steam locomotives: a large Price built in Thames, two Invercargill-engineered Johnstons and a British Barclay.
The mill itself was two storeys high, with the saws and benches on top and massive boilers fired by sawdust beneath. In its heyday it produced more timber than anywhere in the country—up to 1800 cubic metres a month.
In the absence of a good harbour, timber was first carried to offshore traders on 12-metre lighters towed by launches. But after sand built up around the break­water, the overhead cable technology of the Lidgerwood was copied on the wharf. A 21-metre tower was built, and loads of timber were slung, sometimes day and night, on to waiting ships, many of them bound directly for North Island markets, and some to Australia.
At its peak, Port Craig was a town of some 230 people, with the mill employing at least 150 hands. Workers were paid once a month by cheque—to discourage gambling—with the company-run store bill deducted from the wages. Alcohol could be consigned from town, but had to be kept at the store until Saturday, after work had finished.
When workers and their families travelled to town they were ferried across to Bluecliffs Beach by launch, and landed by surf boat.
Today the most spec­tacular relics of Port Craig's logging era are four wooden viaducts built to carry the haulers and locomotives across ravines to the west of the township.
Incredibly, all are still standing. The largest, the Percy Burn, spans 125 metres and stands 36 metres above the stream bed. Buried in the regener­ating forest for 60 years, and virtually unknown outside the district, the Percy Burn viaduct was selected in 1990 as one of New Zealand's 50 great engineering works by the Institute of Professional Engineers of New Zealand.
The viaducts represent the very best of the bridge builder's trade. All are of trestle design, with steel-braced beams of Australian hardwood, probably jarrah.
A cookshop and huts for about 20 men were built at the site, and construction took nearly a year. A cable was slung across the gully from one of the logging haulers, and the bridge components winched across under a carriage and placed in position.
The Percy Burn was the biggest viaduct constructed for a bush tram in New Zealand, and it was the second-longest and second-highest ever built. The largest was the Ormondville viaduct on the Hawke's Bay railway line, demolished 20 years before the Percy Burn was com­ pleted in 1923.
At £5000, the viaduct was expensive, but a cheaper option than building extra tramlines and excavating to maintain a gradient around the head of the stream.
Time is finally beginning to catch up with the Percy Burn viaduct. Some of its supporting beams and trestle legs have rotted out, and wind stress has caused it to buckle. Deterioration was hastened in the 1970s when a pig hunter set fire to the structure. As the story was told in Tuatapere's Waiau Hotel, the hunter had lost a pig dog off the side of the then undecked bridge, and to spare fellow hunters a similar fate he tried to bum it down.
Fortunately, his attempt failed, and shortly after­wards the Forest Service redecked the viaducts to increase safety and improve access for hunters and trampers walking between Port Craig and Waitutu Forest.
Recently the Tuatapere community, Department of Conservation, Southland District Council, Historic Places Trust and New Zealand Army joined forces to carry out repairs on the Percy Burn viaduct. Sol­diers from the Army's Ready Reaction Force abseiled from the deck to brace deteriorating timbers. Under their war gaming scenario, the bridge had been weakened by enemy fire.
In reality, it was the 1920s economic recession which was the death knell for the Port Craig sawmil­ling operation—at that time the largest and most ambitious in the country.
Falling prices and a depressing assessment of the remaining timber resource forced the owners to close the mill on October 6, 1928.
Minty Hughes, like all Port Craig workers, was given four days' notice. When the Bluff Harbour tug, Southland, arrived to pick up residents, they had only a few hours to gather together what they could carry. Many arrived in Invercargill with nowhere to go, and, with the Depres­sion beginning, they had little chance of finding other work.
In 1940 the machinery, mill and houses were sold to a salvage firm and removed. All that remains are the viaducts: unique relics of Southland history.

Brushtail possums are a protected species in their native Australia.Across the Tasman, they have established themselves as New Zealand's most voracious and intrac;.able pest, attacking simultaneously the beauty of our forests and the good name of our farming products.

Fiordland National Park consists of a million hectares of rock and river, forest and fiord—some of the wildest and most untouched country in New Zealand. The place is a magnet to adventurers, who come here from around the world to experience true wilderness.